Later, in the warmer weather, the sperm may be pretty 

 well run off and the reproductive organ contain mostly 

 eggs. In this way the younger oysters, and the older 

 oysters at the beginning of the season, may be physio- 

 logically males, while older oysters at the height of the 

 breeding season may be physiologically females. 



Oysters from Hammond Bay showed the same phe- 

 nomena. 



Upon finding an abundance of larger oysters on the 

 surface at Nanoose Bay, I brought home a pail-full of 

 picked specimens to serve as a convenient stock for ob- 

 servation and experiment. On July 16 I found a speci- 

 men with perhaps half a teaspoonful of eggs in various 

 stages of segmentation, lying free in the lower valve — a 

 mass of white granules. The ripe eggs ooze into the 

 infra-branchial cavity and lie on and between the gills, 

 /. e., between the two folds of the mantle, where they are 

 retained apparently without any retaining, sticky matrix. 

 I suppose that it is here they first meet with ripe sperms 

 from other individuals, for I do not believe that at this 

 time the sperms of the same individual are physio- 

 logically capable. The whole oyster appears exhausted, 

 the gills rent, the flesh collapsed, soft and parts of it 

 almost rotten. On July 24 I opened one hundred of 

 the stock supply and found six with eggs, embryos or 

 conchiferous young, in the infra -branchial cavity. All 

 the others were in process of spermogenesis and 

 oogenesis. 



An experiment that has often seemed possible to me is 

 to do the same with the European oyster, by way of 

 artificial fertilization, as Brooks did with the American 

 oyster. Now that I had an oyster essentially the same as 

 the European I tried it, and with seeming success, but 

 of course it is difficult to be sure that sperm from another 

 had not already had access to the eggs. Unripe eggs 

 are no good; eggs already freed from the gonad may 

 have come in contact with sperm. This restricts one to 

 finding a specimen just before but just on the point of 



